3 files changed, 62 insertions, 0 deletions
diff --git a/pylint/test/functional/comparisons.py b/pylint/test/functional/comparisons.py
new file mode 100644
index 0000000..73067c8
--- /dev/null
+++ b/pylint/test/functional/comparisons.py
@@ -0,0 +1,11 @@
+# pylint: disable=missing-docstring, invalid-name
+x = 42
+a = x is None
+b = x == None  # [singleton-comparison]
+c = x == True  # [singleton-comparison]
+d = x == False  # [singleton-comparison]
+e = True == True  # [singleton-comparison]
+f = x is 1
+g = 123 is "123"
+h = None is x
+i = None == x  # [singleton-comparison]
diff --git a/pylint/test/functional/comparisons.txt b/pylint/test/functional/comparisons.txt
new file mode 100644
index 0000000..fd1fa98
--- /dev/null
+++ b/pylint/test/functional/comparisons.txt
@@ -0,0 +1,5 @@
+singleton-comparison:4::Comparison to None should be 'expr is None'
+singleton-comparison:5::Comparison to True should be just 'expr' or 'expr is True'
+singleton-comparison:6::Comparison to False should be 'not expr' or 'expr is False'
+singleton-comparison:7::Comparison to True should be just 'expr' or 'expr is True'
+singleton-comparison:11::Comparison to None should be 'expr is None'
diff --git a/pylint/test/unittest_checker_base.py b/pylint/test/unittest_checker_base.py
index f19544f..c68f379 100644
--- a/pylint/test/unittest_checker_base.py
+++ b/pylint/test/unittest_checker_base.py
@@ -246,6 +246,52 @@ class MultiNamingStyleTest(CheckerTestCase):
                 self.checker.visit_functiondef(func)
             self.checker.leave_module(func.root)
 
+class ComparisonTest(CheckerTestCase):
+    CHECKER_CLASS = base.ComparisonChecker
+
+    def test_singleton_comparison(self):
+        node = test_utils.extract_node("foo == True")
+        message = Message('singleton-comparison',
+                          node=node,
+                          args=(True, "just 'expr' or 'expr is True'"))
+        with self.assertAddsMessages(message):
+            self.checker.visit_compare(node)
+
+        node = test_utils.extract_node("foo == False")
+        message = Message('singleton-comparison',
+                          node=node,
+                          args=(False, "'not expr' or 'expr is False'"))
+        with self.assertAddsMessages(message):
+            self.checker.visit_compare(node)
+
+        node = test_utils.extract_node("foo == None")
+        message = Message('singleton-comparison',
+                          node=node,
+                          args=(None, "'expr is None'"))
+        with self.assertAddsMessages(message):
+            self.checker.visit_compare(node)
+
+        node = test_utils.extract_node("True == foo")
+        message = Message('singleton-comparison',
+                          node=node,
+                          args=(True, "just 'expr' or 'expr is True'"))
+        with self.assertAddsMessages(message):
+            self.checker.visit_compare(node)
+
+        node = test_utils.extract_node("False == foo")
+        message = Message('singleton-comparison',
+                          node=node,
+                          args=(False, "'not expr' or 'expr is False'"))
+        with self.assertAddsMessages(message):
+            self.checker.visit_compare(node)
+
+        node = test_utils.extract_node("None == foo")
+        message = Message('singleton-comparison',
+                          node=node,
+                          args=(None, "'expr is None'"))
+        with self.assertAddsMessages(message):
+            self.checker.visit_compare(node)
+
 
 if __name__ == '__main__':
     unittest.main()